Method and system for automated fatigue and structural analysis of an element

ABSTRACT

A method, system and computer program product are provided for automated fatigue and structural analysis of a structural element. The method, system and computer program product consolidate and manage the fatigue and structural analysis tools and are responsive to user requests for fatigue and structural analysis of elements based upon user-provided information regarding the element. As such, the appropriate fatigue and structural analysis tools are automatically selected and run, and the output of the tools is automatically evaluated to provide immediately useful fatigue and structural analysis results to the user without requiring further manual input. Thus, people without specialized training can quickly obtain fatigue and structural analysis results for an element. In addition, because the fatigue and structural analysis tools are integrated, the tools may be accessed from remote locations via a computer network.

FIELD OF THE INVENTION

This invention relates to fatigue and structural analyses and, moreparticularly, to a method, system and computer program product,typically embodied in an Internet-based solution, that provides forautomated fatigue and structural analysis to generate results, such asmargins of safety.

BACKGROUND OF THE INVENTION

Structural components such as airframes, automobiles, bridges, etc., aresubjected to various types of forces throughout their intended designlife. These forces create stresses in the structure that can eventuallycause wear, damage, and the possible failure of the structure. As such,fatigue and structural analysis of many structural components(structural components is also referred herein as structural elements orelements) is important during the design process. Fatigue and structuralanalyses provide structural designers with critical information used todetermine the likelihood and the causes of fatigue related structuralfailures. Once the structural designers have the results of the fatigueand structural analyses, they can design the individual elements and theoverall structure so as to withstand the anticipated stress levels overthe design lifetime.

Fatigue and structural analyses are particularly important forstructures that are subject to extreme forces over the lifetime of thestructure. For instance, aircraft structures experience a variety ofintense forces as they repeatedly take off, fly, perform variousmaneuvers and land over the lifetime of the aircraft. These forcescreate stresses internally in the structure, which may cause wear,damage, and possible failure of the structure if it is not properlydesigned to withstand the anticipated stresses.

In general, fatigue and structural analyses are performed using a seriesof analysis tools. The tools typically include customized computerprograms for a specific structural design (e.g., an F-15 fighteraircraft). The programs typically do not interact with each otherdirectly and are often hosted on computer platforms that cannotcommunicate with one another. As such, specially trained analysts mustbe involved throughout the design process to check, modify, andtranslate the inputs and outputs of each computer program. The fatigueand structural analysis process is time consuming and inefficientbecause designers must delay their structural design work untilspecially trained fatigue analysts develop “fatigue allowables” (themaximum repeated stress a structural component can withstand withoutfailure) for each specific structural element. Development of thefatigue allowables is time consuming because it involves determining theanticipated loading throughout each component's design life, generatingthe fatigue life prediction of each component based on the loading andmaterial properties of the component, and relaying this information backto the structural designer. The designer must then compute the maximumstress in the component based on its current configuration and comparethat stress to the fatigue allowable. If the component is determined tohave an inadequate fatigue life, the designer must change theconfiguration of the component and repeat the maximum stress analysisprocess.

The fatigue and structural analysis processes used in the past are alsoinflexible because they are tailored to specific computer platforms.And, typically, there are multiple computing platforms involved in theprocess requiring translation of intermediate results to differentcomputer platforms that are not compatible with one another. Forexample, when developing the fatigue allowables, different computerapplications are generally required to determine the anticipated loadingthroughout each component's design life, generate the fatigue lifeprediction of each component based upon the loading and materialproperties of the component, and compute the maximum stress in thecomponent based upon its current configuration.

For the reasons discussed above, there exists a need for an automatedfatigue and structural analysis system that combines and manages theseparate fatigue and structural analysis tools such that analystswithout specialized training and on various computer platforms mayquickly obtain useful fatigue and structural analysis results.Specifically, the need is for a fatigue and structural analysis systemthat automatically accesses and runs the appropriate fatigue andstructural analysis tools to quickly analyze user-provided informationregarding a structural component and provide an immediate report of thefatigue and structural analysis results without further manual input.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method, system and computerprogram product, typically embodied as an Internet-based solution, areprovided for automated fatigue and structural analyses. The method,system and computer program product consolidate and manage the fatigueand structural analysis tools and are responsive to user requests forfatigue and structural analyses based upon user-provided information. Assuch, the method, system and computer program product of the presentinvention automatically select and run the appropriate fatigue andstructural analysis tools, and automatically evaluate the outputs of thetools to provide immediately useful fatigue and structural analysisresults to the user without requiring further manual input. Thus,designers without specialized training can quickly obtain fatigue andstructural analysis results. In addition, because the method, system andcomputer program product of the present invention consolidate and managethe fatigue and structural analysis tools, the tools may be accessedfrom remote locations via the Internet, intranet or other computernetwork. The method, system and computer program product of the presentinvention, therefore, save time and increase the efficiency of thedesign process by opening up the process to designers and eliminatingthe delay that would otherwise be caused by manually performing fatigueand structural analyses by specially trained analysts.

The method, system and computer program product for automated fatigueand structural analyses of the present invention receive a request toperform fatigue and structural analyses based upon information regardingthe structural element of interest. In this regard, the system mayinclude a client component (e.g., a web browser) for receiving theinformation. Based upon the information regarding the structuralelement, the method, system and computer program product of the presentinvention automatically perform the fatigue and structural analyseswithout requiring further manual input and automatically provide theresults of the fatigue and structural analyses. In this regard, thesystem may also include a processing component (e.g., a server) forautomatically performing the fatigue and structural analyses andautomatically providing the results of the fatigue and structuralanalyses to the client component.

Embodiments of the method and system of the present invention also maystore the results of the fatigue and structural analyses in a storageelement. Other embodiments of the method of the present inventioninclude determining dimensions of the structural element and thematerial composition of the element based upon the results of thefatigue and structural analyses.

In one advantageous embodiment of the method, system and computerprogram product of the present invention, the fatigue analysis includesautomatically determining a fatigue allowable for the structural elementand automatically determining the actual maximum stress in the element.The fatigue allowable for the structural element may be calculated bydetermining an anticipated loading of the structural element over timeand, based upon the anticipated loading of the structural element overtime, determining the maximum allowable stress to which the structuralelement may be subjected. The actual maximum stress for the structuralelement may be determined by applying a reference load to the structuralelement to ascertain the actual stress to which the structural elementwill be subjected. The method, system and computer program product ofthe present invention then automatically compare the actual maximumstress to the fatigue allowable to determine the margin of safety forthe structural element.

The method, system and computer program product of the present inventiondescribed herein saves time and increases the efficiency for designprocesses that require fatigue and structural analyses because thepresent invention is automated to quickly provide fatigue and structuralanalysis results. Without the automated features of the presentinvention, a specially trained analyst would have to manually performthe separate fatigue and structural analyses and manually evaluate theoutputs of the analyses to determine and provide the necessary fatigueand structural analysis results before the design process could proceed.

Other useful embodiments of the method, system and computer programproduct permit the implementation of the present invention via theInternet, intranet or other computer network. Specifically, the systemof one embodiment of the present invention includes a client component(e.g., a web browser) and a processing element, such as a server, thatare remote from one another and the Internet, intranet or other computernetwork for interconnecting the client component and the processingelement. The system of this embodiment of the present invention may alsoinclude a plurality of distributed client components interconnected tothe processing elements via the Internet, intranet or other computernetwork. Regardless of the configuration, each client component maypresent at least one web page to solicit the required information forfatigue and structural analyses. As such, the required information andthe request to perform fatigue and structural analysis may be receivedfrom a plurality of distributed clients based upon information inputinto the respective web pages. The required information and the requestto perform fatigue and structural analysis would then be transmittedfrom the plurality of distributed clients to one or more commonprocessing components via the Internet, intranet or other computernetwork.

These useful embodiments of the method, system and computer programproduct of the present invention further reduce the time and increasethe efficiency of the design process because they enable the features ofthe present invention to be performed from different locations via theInternet, intranet or other computer network and in aplatform-independent manner. These embodiments are significantimprovements over the time consuming and inefficient fatigue andstructural analysis previously performed by specially trained analystson specific workstations with manual evaluation of the results beforethe design process may proceed.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a block diagram illustrating the operations performed by themethod, system and computer program product, of one embodiment of thepresent invention;

FIG. 2 is a flow diagram illustrating the operations of one example of aload spectrum generation application as performed by the method, systemand computer program product of one embodiment of the present invention;

FIG. 3 is a flow diagram illustrating the operations of one example ofan allowable stress development application as performed by the method,system and computer program product of one embodiment of the presentinvention;

FIG. 4 is a block diagram illustrating some of the operations of oneexample of an actual stress development application as performed by themethod, system and computer program product of one embodiment of thepresent invention;

FIG. 5 is a representative display provided by the client interface ofthe general types of elements on which the detail stress analysis may beperformed according to one embodiment of the present invention;

FIG. 6 is a representative display provided by the client interface thatprompts the user to input information regarding the element and thereference condition on which actual stress fatigue analysis is requestedaccording to one embodiment of the present invention;

FIG. 7 is a representative display provided by the client interface ofthe results of the actual stress fatigue analysis that provide thelocation and measurement of the maximum actual stress experienced by theelement at a certain reference condition according to one embodiment ofthe present invention;

FIG. 8 is a representative display provided by the client interface ofthe types of allowable stress fatigue analysis that may be performed onan element at a reference condition according to one embodiment of thepresent invention;

FIG. 9 is a representative display provided by the client interface thatprompts the user to input information regarding the element and thereference condition on which finite element based allowable stressfatigue analysis is requested according to one embodiment of the presentinvention;

FIG. 10 is a representative display provided by the client interface ofthe results of the allowable stress fatigue analysis at a certainreference condition according to one embodiment of the presentinvention; and

FIG. 11 is a representative display provided by the client interface ofthe summary of the stress analysis that includes the actual stressfatigue analysis, the allowable stress fatigue analysis, and the marginof safety calculation result according to one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Fatigue and structural analyses are a fundamental component of themodern structural design process. Structural items such as automobiles,bridges, and aircraft carry loads that vary over time. These structuralitems are required to operate without failure for a specified life.Performing fatigue and structural analyses allows the structuraldesigner to estimate the life of a structure or to design a structure tomeet a required design life.

Fatigue and structural analyses are typically performed for a particulardetail within a structural element. Examples of details include fastenerholes, cutouts and fillets. As a result of its application to aircraft,the present invention will be primarily described hereinafter inconjunction with fatigue and structural analyses of aircraft. However,the present invention is also useful for the fatigue and structuralanalysis of a number of other structures as will be apparent to thoseskilled in the art.

In accordance with the present invention, a method, system and computerprogram product are provided for automated fatigue and structuralanalysis of structural elements. The method, system and computer programproduct consolidate and manage fatigue and structural analysis tools andare responsive to user requests for fatigue and structural analysisbased upon user-provided information regarding the structural detail inquestion. As such, the method, system and computer program product ofthe present invention automatically select and run the appropriatefatigue and structural analysis tools and automatically evaluate theoutputs of the tools to provide immediately useful fatigue andstructural analysies results to the user without requiring furthermanual input. Thus, users without specialized training can quicklyobtain fatigue and structural analysis results. In addition, because themethod, system and computer program product of the present inventionconsolidate and manage the fatigue and structural analysis tools, thetools may be accessed from remote locations via the Internet, intranetor other computer network. The method, system and computer programproduct of the present invention, therefore, save time and increase theefficiency of the design process by eliminating the delay that wouldotherwise be caused due to manually performing fatigue and structuralanalyses by specially trained analysts using several separate tools.

FIG. 1 is a block diagram of the method, system 20 and computer programproduct of one embodiment of the present invention. The system 20typically includes a client component 22 and a processing component. Asshown in FIG. 1, the processing component of one embodiment may have twoportions, a web server 24, and an application server 26. The clientcomponent and the processing component may be part of a singleworkstation, computer, server or other computing device and, as such,may communicate with each other via internal transmissions.Alternatively, the client component and the processing component and, inone embodiment, the web server and the application server of theprocessing component may be distributed as parts of differentworkstations, computers, servers or computing devices that may be indifferent physical locations and in communication with each other viathe Internet, intranet or other computer network. To be consistent, thediscussion hereinafter refers to the different components of the system20 as being distributed, unless otherwise stated. The fatigue analysissystem 20 also includes a database 38 that may be part of the clientcomponent, the processing component, or most likely, may be separatefrom both the client and processing components and in communication withone or both of the components via the Internet, intranet or othercomputer network. Regardless of the configuration, the database 38 isaccessed by other parts of the fatigue analysis system 20 via aninterface, such as active data object (ADO) interface or open databaseconnectivity (ODBC) interface.

The client component 22 represents the device that includes theinterface 28 that users of the automated fatigue analysis system 20 mayutilize to request fatigue analysis for a detail of an element (hole,notch, or other structural detail). In the implementation discussedherein, users may request the fatigue allowable, the actual maximumstress in a structural element or the margin of safety. The system couldbe extended to include automation of any other aspect of fatigue andstructural analysis such as sonic fatigue, composite analysis, andbuckling. The client component may be a personal computer or workstationoperating on any type of computer platform and the interface 28 may beany type of Internet browser. The system 20 may include many clientcomponents 22 such that many users may utilize the fatigue analysissystem 20. The client component(s) 22 may physically be located anywhereas long as the client component(s) 22 are in communication with theprocessing component via the Internet, intranet or other computernetwork.

As described above, the processing element of one advantageousembodiment includes a web server 24, which may utilize any modernoperating system, such as Microsoft Windows. Among other functions, theweb server 30 provides active server pages 30 to the client component22, which displays the active server pages 30 for the user via theinterface 28. As known to those skilled in the art, the active serverpages 30 are interactive forms that prompt the user for the informationnecessary for the fatigue analysis system 20 to perform fatigue analysison the structural detail of interest. After the user submits responsesto the prompts in the first active server page, the web server 24determines the content and prompts contained in the successive activeserver pages based upon the user responses to the prompts contained inthe previous active server page or pages.

In the illustrated embodiment, the web server submits the fatigueanalysis request to a fatigue analysis manager module 32 via internalserver communications, such as via Microsoft's component object module(COM). The fatigue analysis manager module 32 receives the informationregarding the element that has been collected by the active server pages30 and, if necessary, properly formats the information for the fatigueanalysis. The fatigue analysis manager module 32 then puts the fatigueanalysis request and element information in a queue that is monitored bythe application server. The fatigue analysis manager module 32 alsomonitors the queue for fatigue analysis results posted to the queue bythe application server. Once the fatigue analysis manager module 32identifies that fatigue analysis results have been put in the queue andextracts the fatigue analysis results form the queue, the web serverpopulates or otherwise configures one or more active server pages 30with the results of the fatigue analysis. The web server then transmitsthese active web pages to the client component 22 for display to theuser via the interface 28.

Although the application server may be configured in different manners,the application server 26 of the illustrated embodiment includes afatigue analysis manager service 34 and a fatigue analysis manager agent36. The application server may utilize any modern operating system. Thefatigue analysis manager service 34 monitors the queue for fatigueanalysis requests placed in the queue by the fatigue analysis managermodule 32. The fatigue analysis manager service 34 and the fatigueanalysis manager module 32 communicate via any standard queuingtechnology, such as Microsoft Message Queue (MSMQ). When the fatigueanalysis manager service 34 sees a fatigue analysis request in thequeue, it delivers the request to the fatigue analysis manager agent 36via internal server communications, such as via Microsoft's componentobject module (COM).

The fatigue analysis manager agent 36 receives the fatigue analysisrequest and the corresponding information regarding the structuraldetail and determines which fatigue analysis tool(s) to run to performthe desired type of fatigue analysis. The fatigue analysis tools areillustrated as 40, 42, and 44 in FIG. 1 as a specific example that isdiscussed herein, but any fatigue analysis tool or combination offatigue analysis tools may be selected and utilized by the fatigueanalysis manager agent 36. The fatigue analysis manager agent 36determines the proper fatigue analysis tool(s) based upon the type offatigue analysis requested. In this regard, the fatigue analysis manageragent 36 is typically preprogrammed with the fatigue analysis tool(s) tobe utilized to perform different types of fatigue analysis. The fatigueanalysis manager agent 36 also provides the appropriate fatigue analysistool(s) with the information regarding the element and receives theoutput(s) from the fatigue analysis tool(s). The fatigue analysismanager agent 36 communicates with the various fatigue analysis toolsthat may be located either on the same or other servers or computingdevices by any standard inter-machine communication, such as Microsoft'sdistributed component object module (DCOM).

If the desired type of fatigue analysis requires that the outputs of thefatigue analysis tool(s) be further processed to obtain the fatigueanalysis results, then the fatigue analysis manager agent 36 alsotypically performs those functions. Once the fatigue analysis manageragent 36 determines the fatigue analysis results, whether the resultsare the direct output of a particular fatigue analysis tool or acomputation performed by the fatigue analysis manager agent 36, itstores the results in the database 38, and transmits the results to thefatigue analysis manager service 34. The fatigue analysis managerservice 34 then puts the results on the queue for the fatigue analysismanager module 32 to pick up. The active server pages 30 may then bepopulated or otherwise configured based upon the results prior to beingprovide to the client component 22 for display to the user via theinterface 28. Thus, the method, system and computer program product forautomated fatigue and structural analysis of a structural element of thepresent invention quickly provide users with immediately useful fatigueanalysis results for a structural element. In addition, the method,system and computer program product of the present invention enableusers, who are not in the same location as the fatigue analysis toolsand not trained on the use of the fatigue analysis tools, to obtain thefatigue analysis results that are necessary for a structural designprocess to proceed in a timely and intuitive manner.

The determination of a fatigue margin of safety is one type of aircraftfatigue analysis that is performed on details within structural elementsto determine if the elements can withstand the extreme forces to whichthe aircraft is subjected over its lifetime. Other types of analysesthat could be performed include, for instance, sonic fatigue, buckling,and static strength analysis. In general, margin of safety fatigueanalysis is performed by a series of fatigue analysis tools thatsimulate the forces to which the aircraft is exposed, evaluates theresponse of the elements to the forces over the lifetime operation ofthe aircraft, and predicts the life of the structure or calculates anallowable stress. The tools may be a combination of custom builtapplications for the specific aircraft and separately configuredcommercial applications. In this regard, although exemplary fatigueanalysis tools will be described below for purposes of illustration, itshould be understood that those skilled in the art will be familiar witha number of fatigue analysis tools that may be integrated in accordancewith the present invention. With respect to a margin of safety, however,the margin of safety equation for a structural element is defined as:$\frac{{Maximum}\quad {Allowable}\quad {Stress}}{{Actual}\quad {Stress}} - 1$

wherein the maximum allowable stress and the actual stress aredetermined at the same reference condition for the structural element atissue. The maximum allowable stress is the largest stress that may occurin the structural element without resulting ill a premature failure.

FIG. 1 illustrates the communication of the fatigue analysis manageragent 36 with the fatigue analysis tools necessary to perform the marginof safety fatigue analysis for the element. As shown, these fatigueanalysis tools are a load spectrum application 42, an allowable stressapplication 44, and an actual stress application 40. The fatigueanalysis manager agent 36 receives the outputs of the fatigue analysistools 40, 42 and 44 and, based upon the outputs, determines the marginof safety for the element.

The load spectrum application 42 develops a load fatigue spectrumspecifically for the structural element of interest. The load spectrumapplication 42 is typically a computer program developed for theparticular type of structure, such as an aircraft, that contains theelements at issue. To develop the load spectrum, information regardinghow the structure is utilized over the target life of the structure andestimates of all of the forces to which the structure is subjected byits use are provided to the load spectrum application 42. As describedbelow, the anticipated use of the structure is typically defined by aseries of maneuvers or activities, each of which will impose a set offorces upon the structure and, in turn, the elements that make up thestructure. In addition, the target life of the structure is the amountof time that the designers of the structure desire the structure toproperly function prior to failure. Based upon the combination of forcesto which the structure is subjected over time, the load spectrumapplication 42 then produces the total loads to which the structure issubjected along a time axis that represents the lifetime of thestructure.

By way of example, a load spectrum application 42 developed by TheBoeing Company called a Rapid Spectrum Generator (Raptor) will bedescribed, although those skilled in the art will be familiar with othersuitable load spectrum applications. FIG. 2 is a flow diagramillustrating the operations of the Raptor application 50 to generate aload spectrum 58 for element R, which is an element, i.e., a rod,representing a portion of the wing component of an aircraft. Element Rmight include a portion of the wing skin, wing spar caps, and webs. Togenerate the load spectrum 58, the Raptor application 50 first evaluatesa master event spectrum 52 for the type of aircraft structure thatcontains the element R. The master event spectrum 52 for an aircraft isa sequence of maneuvers that the aircraft experiences over the life ofthe aircraft, such as take offs and landings or any other in-flightmovements such as rolls, dives and the like. Based upon the master eventspectrum, each maneuver is simulated and the collection of forces towhich the aircraft is subjected during each maneuver is captured. Forexample, the forces on the aircraft 54 during maneuver A are Force A,Force B and Force C. Points in time during the course of performingmaneuver A are selected, which are represented as A1, A2, A3, A4 and A5.For each point in time, the load imposed upon element R as a result ofthe collection of forces upon the aircraft is determined based upon apredefined finite element model 56 for the aircraft. As such, a loadspectrum 58 is created for the element R representing the load onelement R at each point in time. This load spectrum can be used todetermine the fatigue life and margin of safety for any actualstructural detail represented by element R.

One example of an allowable stress application 44 uses the load spectrumcreated by the load spectrum application 42 to determine how much loadthe structure can withstand over its predefined lifetime prior tofailure. Thus, the allowable stress application 44 creates an allowablestress spectrum for the element of the structure based on the loadspectrum for the element of the structure.

One type of allowable stress application 44 is the LifeWorks application60 developed by The Boeing Company, although those skilled in the artwill be familiar with other suitable allowable stress applications. Todetermine the allowable stress for element R, the LifeWorks application60 selects a reference point, such as load condition A1, and estimates astress level for the load at time A1. See blocks 62 and 64. The LifeWorks application 60 then estimates the stress levels for the loads atthe other times on the spectrum, A2-A5, by scaling the loads inaccordance with the load-to-stress ratio established by the estimatedstress level for the load at time A1. See block 66. From the stressspectrum that is created by scaling, the LifeWorks application 60determines the estimated fatigue life of the element, represented by 68.

If the estimated fatigue life equals the target life of the element,then the estimated stress spectrum is the correct allowable stressspectrum. As mentioned above, the target life of the element is theamount of time that the designers of the structure desire the element ofthe structure to function prior to failure. If, however, the estimatedfatigue life does not equal the target life of the element, then theestimated stress level at condition A1 is adjusted. The resulting stressspectrum is accordingly adjusted based upon the new load-to-stress ratioand the fatigue life is, in turn, determined again. Thus, if theestimated fatigue life is longer than the target life, the estimatedstress level at time A1 should be increased, which will accordinglyincrease the estimated stress spectrum and shorten the estimated fatiguelife. If the estimated fatigue life is shorter than the target life, theestimated stress level at time A1 should be decreased, which willaccordingly decrease the estimated stress spectrum and lengthen theestimated fatigue life. This type of iterative process, represented by70 and 74, continues until the estimated stress spectrum results in theestimated fatigue life of the element equaling the target fatigue lifeof the element or, in some embodiments, exceeding the target fatiguelife by no more than a predetermined amount. The resulting stressspectrum is the allowable stress spectrum for the element, representedby 72. Because the allowable stress spectrum is based on the loadspectrum 58, it is specific to the particular material and particularelement defined by the finite element model 56. The allowable stressspectrum results are transmitted to the fatigue analysis manager agent36, which may store the results in the database 38 and transmit theresults back to the web server and, in turn, the client component viathe process described hereinabove.

If the user has requested that the fatigue analysis manager agent 36determine the margin of safety, the fatigue analysis manager agent 36will also use the results, in addition to the results from other fatigueanalysis tool(s), for the margin of safety calculation. To determine themargin of safety for an element, the fatigue analysis manager agent 36not only obtains the allowable stress spectrum by utilizing the loadspectrum application 42 and the allowable stress application 44, theagent 36 also must obtain the actual maximum stress the elementexperiences by utilizing the actual stress application 40. The actualstress application 40 may utilize finite element techniques or otherautomated engineering analysis to calculate the actual stress at variousdetail locations on the element of the structure. The actual stressapplication 40 determines the maximum actual stress on the element inresponse to the imposition of the collection of forces at a particularpoint in time.

One type of actual stress application 40 is the StressCheck applicationthat is commercially available from Engineering Software Research &Development, Inc. FIG. 4 is a block diagram representation of theoperations performed by the StressCheck application 80. The StressCheckapplication 80 utilizes the collection of forces imposed upon element Rat a particular point in time, such as time A1, to determine the actualstresses on a specific structural detail included in element R for thatload. This detail might be a fastener hole, a notch, or a fillet. Todetermine the actual stresses on the detail, the StressCheck application80 analyzes the geometry of the structural detail represented by elementR in detail as the load is applied and creates a detailed representationof the actual geometry and the levels of stress at different locationsupon or about element R, as represented by 82. As opposed to the overallor more general analysis of element R provided by the allowable stressapplication, the StressCheck application can provide the exact locationof the maximum stress experienced by the structural element, representedby 84. The actual stress results are transmitted to the fatigue analysismanager agent 36, which may store the results in the database 38 andtransmit the results back to the web server and, in turn, the clientcomponent via the process described hereinabove. If the user hasrequested that the margin of safety be determined, the fatigue analysismanager agent 36 will also use the results, in addition to the resultsfrom other fatigue analysis tool(s), i.e., from the allowable stressapplication, for the margin of safety calculation as defined above.

FIGS. 5 through 11 further illustrate the features of the method, system20 and computer program product of one embodiment of the presentinvention. The figures demonstrate the embodiment of the presentinvention that performs automated stress fatigue analysis and margin ofsafety calculations. In the examples to follow, the figures arerepresentative of the displays of the active server pages 30 that a usermay view and with which a user may interact via the interface 28 of theclient component 22.

FIG. 5 is a representation of the display 90 via the client interface28, shown as Microsoft Internet Explorer in this embodiment of thepresent invention, of an active server page 30 that permits a user torequest fatigue stress analysis and margin of safety calculations for anelement of a structure. In the upper portion 92 of the display 90, theuser may select the type analysis. “Detail Stress” represents a requestfor an actual stress analysis to determine the maximum actual stressexperienced by an element and the location of the maximum actual stressin the element. “Allowable” represents a request for an allowable stressanalysis to determine the allowable stress the element can withstandprior to failure. “Title” permits a user to identify a particularanalysis for future reference or the like. “Summary” represents arequest for a summary of the types of stress analyses performed on theelement and a margin of safety calculation for the element. “Save/Open”represents a request to save or open an existing stress analysis file.“DaDT Home” represents a request to return to a designated home page.The lower portion 94 of the display 90 illustrates the screen when auser selects “Detail Stress” from the upper portion 92. These optionsare the same in the displays represented in FIGS. 6-10.

The screen of the lower portion 94 permits the user to select thegeneral type of element on which the detail stress analysis isrequested. The elements listed will vary based upon, among otherfactors, the type of structure being analyzed. In this example, however,types of holes, fillets and cutouts contained in the element are listedbecause the majority of stress damage occurs around these types ofopenings. When the user brushes over a type of hole, fillet or cutoutthat is listed with a pointer or cursor, a picture of the type of hole,fillet or cutout is presented on the screen. In FIG. 5, the user brushedover “One Free Edge” listed under “Holes” and a picture showing a holein an element having one edge without a load is displayed on the screen.

When the user selects “One Free Edge” from the list under “Holes” thatis shown in FIG. 5, the web server generates an active server page 30that is presented to the user as shown in FIG. 6. The screen 96 in FIG.6 prompts the user to enter information regarding the element for whichactual stress fatigue analysis is requested and to define the referencecondition for the analysis. The upper left-hand portion of the screen 96under the “Geometry” heading prompts the user to enter the dimensions ofthe element and the hole in the element, including the dimensions of thecountersink (cs), if any. The upper middle portion of the screen 96under the “Geometry” heading prompts the user to select and enterinformation regarding the hole in relation to the existence of otherholes. In the “Hole Type” area, the user may choose “Single,”“Intermediate,” or “End.” “Single” indicates that the structural detailhas no other hole near the hole in question. “Intermediate” indicatesthat the hole is somewhere in the middle of a row of holes in theelement. “End” indicates that the hole is on the end of a row of holes.If the user selects “Intermediate” or “End” the user must enter thecenter-to-center spacing between the hole at issue and next closest holein inches in the “Pitch” area. If appropriate the user can describe thehole in relation to other holes, as described above, in the x-Directionand the y-Direction.

The upper right-hand portion of the screen 96 under the “Geometry”heading prompts the user to select and enter information regarding thefastener, if any, that is in the hole and the material of the element.The “Joint Type” area prompts the user to select “Clamped,” “Unclamped,”or “N/A.” “Clamped” indicates that the hole extends through two platesand a torqued fastener connects the plates through the hole. “Unclamped”indicates that a loose fastener connects two plates through which thehole extends. “N/A” indicates that no fastener is in the hole. The useris also prompted to enter the modulus of elasticity of the element inthe “Plate E” area. If the user selected “Clamped” or “Unclamped” in the“Joint Type” area, the user must also enter the modulus of elasticity ofthe fastener in the “Fastener E” area.

The upper portion of the screen 96 also has a button that the user canselect to “Override Factors.” The effect of the joint type and hole typeis managed through the use of correction factors applied to the resultsof the StressCheck application 80. These factors are typicallydetermined with the fatigue analysis manager agent 36 based uponclosed-form solutions, as known to those skilled in the art. The expertuser may override these factors using the override button.

The lower portion of the screen 96 prompts the user for “Loading”information regarding the element with the type of hole indicated. Theloading information defines the actual loads that act upon the elementat a certain point in time. Thus, the loads entered into the lowerportion of the screen 96 define the forces that act upon the element inresponse to the collection of forces imposed upon the structure at thepoint in time selected as the reference for the actual stress analysis.Typically, the forces are determined by static analysis external to thismethod, system, and computer program product using standard methodsfamiliar to those skilled in the art. However, the actual stressapplication may be designed to determine the forces acting upon theelement based upon the collection of forces imposed upon the structureat the point in time selected as the reference for the actual stressanalysis. “Px” prompts the user for the forces acting upon the edges ofthe element in a predefined x-direction. “Bx” and “By” prompt the userfor the bearing forces acting upon the periphery of the hole in the xand y directions, respectively. “SBx” prompts the user for the bearingforce that acts on the hole in the predefined x-direction and is reactedby shear forces upon the three edges of the element. Depending upon theelement, the user may be prompted to provide other forces, such as Pyand SBy, in addition to or instead of the forces depicted in FIG. 6.

Once the user selects and enters all of the appropriate information onthe display 96, the user may select the “Submit” button, which initiatesthe automated fatigue analysis for the element as described hereinabove.The fatigue analysis manager agent 36 ultimately receives the userrequest and element information and automatically selects the fatigueanalysis tool to perform the detail stress analysis, which may be anactual stress application 40, such as the StressCheck application 80.When the fatigue analysis manager agent 36 receives the results from thefatigue analysis tool, it stores the results in the database 38 andtransmits the results to the fatigue analysis manager service 34 andfatigue analysis manager module 32. The fatigue analysis manager module32 populates the active server pages 30 with the results for the user toview via the client interface 28.

FIG. 7 represents the display of the results of the stress analysis thatthe user may receive. The screen 100 depicts the results in twosections, a detailed visual representation of the actual geometry andthe various levels of stress at locations upon or about the element, asrepresented by 102, and textual information regarding the maximum stressand its location, as represented by 104. The detailed visualrepresentation 102 indicates to the user that the greatest levels ofstress occur on opposite sides of the hole, i.e., on the top and bottomsides, as indicated by 106. The textual information 104 identifies thesection of the element where the maximum stress is located, which is the“MID PLANE” section in this example. The “Angle” value is the anglearound the hole from a reference location where the maximum stress islocated, which is “90 degrees” in this example, i.e., at the bottom ofthe hole. The “Kc/Kt” value is the inverse of the absolute value of theratio of stress resulting from the specified loading to the stressresulting when all specified loads are reversed (applied in the oppositedirection). The “convergence (error)” value is a statistical confidencevalue provided by the fatigue analysis tool. The “Ktσ” value is themaximum actual stress value based on the specified loads for thisreference condition.

The user may also request the allowable stress value for the element, ifdesired, by selecting the “Allowable” button in the upper portion 92 ofthe display. FIG. 8 is the display generated by the web server andpresented by the client component after selecting the “Allowable”button. The display 110 that the user views allows the user to select atype of allowable stress fatigue analysis. For instance, if the loadspectrum application 42 and/or finite element model have not yet beendeveloped for the specific structure and elements for which fatigueanalysis is desired, the user may select the “Component Load BasedAllowable” button. The component load based analysis determines theallowable stress for an element based upon the estimated loads that acomponent of the structure containing the element experiences. Forexample, a component of an aircraft may be the wing, tail or part of thebody. The user selects and enters information regarding the componentthat contains the element at issue and also enters the reference valuefor the analysis. The reference value is a load value that correspondsto the load values provided in the detail stress analysis as describedhereinabove. Thus, the component load based analysis is a generalanalysis of the allowable stress for the component of the structure thatcontains the element, that may be appropriate in the early stages of thedesign process before the information needed to generate the loadspectrum for the structure is gathered and, perhaps, before a detailedfinite element model has been developed.

The display 110 also includes a “Query Allowable Database” button. Thisoption permits the user to query the database 38 that stores theprior-performed allowable stress analyses to determine if the allowablestress analysis results already exist for the element or component atissue and, if so, to retrieve the results of the prior allowable stressanalysis.

The user also may select the “Finite Element Based Allowable” buttonwhen the load spectrum application 42 and finite element model have beendeveloped for the specific structure and its elements to enable a loadspectrum to be generated for the element at issue as explainedhereinabove. When the user selects the “Finite Element Based Allowable”button and requests allowable stress analysis, the display shown in FIG.9 is generated by the web server and provided by the client component onthe client interface 28. The display 120 prompts the user to select andenter the information regarding the element for which allowable stressanalysis is requested. In the “Spectrum Type” area, the user is promptedto select the type of master events upon which the load spectrum for theparticular element is based. Types of spectra include flightmaneuvering, taxi and ground handling. These events comprise the masterevent spectrum 52 as explained. The “Reference Condition” area promptsthe user to select a reference condition from the load spectrum for theelement, such as the conditions existing at time A1-A5 referred to inthe above discussion. The reference conditions may be assigned any typeof identifier, such as the “EFT09P7V3A” identifier of the referencecondition selected in display 120 which corresponds to the conditionsexisting at time A1. The reference condition that the user selects maybe identical to the reference condition that defines the loading, i.e.,the forces, entered in the detail stress analysis. To compare theresults of the allowable and the actual stress analysis, such as in asubsequent margin of safety calculation, the actual stress may beratioed to match the reference condition of the allowable. The“Equation” area of the display 120 permits the user to identify thespecific element or elements and load components to be analyzed. Forinstance, the element at issue in the example shown in FIG. 9 is a roddesignated “112” and it carries a load “Fx,” which is an axial loadonly. As known to those skilled in the art, a number of element typesare available in finite elements and each element type can carry one ormore different types of load, e.g., axial load, shear, moment, ortorque. The user can specify any mathematical relation includingmultiple elements and multiple load components. One example would be tocalculate the load spectrum based on the average of several finiteelements near the detail of interest. This equation would be of the form

([101_Fx]+[102_Fx]+[103_Fx]+[104_Fx])/4

wherein 101, 102, 103, and 104 are individual finite elements such asrods or bars. Another example would be a detail that sees stresses thatare a function of both axial load and bending moment, “Mx.” The exactformulation of the equation would be determined by engineering analysis,as will be apparent to those skilled in the art. An example of thisequation would be of the form:

0.56*[45_Fx]+0.123*[45_Mx]

Display 120 further prompts the user to select a material type of theelement in the “Material” area. The user then selects the detail typethat is located in the element in the “Detail Type” area, whichindicates the type of correction factors that the fatigue analysisprogram may use. If the element contains a shallow gradient, then thestress concentration at the detail is entered in the “Shallow GradientKt” area. The radius of the hole or notch, which matches the dimensionof the hole entered in display 96 of FIG. 6, is entered in the “Hole orNotch Radius” area of display 120. In addition, the user may define oneor more Kc/Kt values. Kc/Kt is defined as the ratio of the stress at adetail under a specified set of loads to the stress at the same detailwhen the specified set of loads are reversed

Alternatively, the web server may generate the active server pages 30 soas to automatically populate the “Detail Type,” “Shallow Gradient Kt,”“Hole or Notch Radius,” and “Kc/Kt” areas based on the informationselected and entered for and the results of the detail stress analysis,if available. If the active server pages 30 are automatically populated,the user may nevertheless override those values with manually enteredinformation.

Once the user selects and enters all of the appropriate information onthe display 120, the user may select the “Submit” button, whichinitiates the automated fatigue analysis for the element as describedhereinabove. The fatigue analysis manager agent 36 ultimately receivesthe user request and element information and automatically selects thefatigue analysis tool(s) to perform the allowable stress analysis, whichmay be an allowable stress application 44, such as the LifeWorksapplication 60. When the fatigue analysis manager agent 36 receives theresults from the fatigue analysis tool, it stores the results in thedatabase 38 and transmits the results to the fatigue analysis managerservice 34 and fatigue analysis manager module 32. The fatigue analysismanager module 32 populates the active server pages 30 with the resultsfor subsequent transmission to the client component for the user to viewvia the client interface 28.

FIG. 10 represents the display of the results of the allowable stressanalysis that the user may receive. Display 122 has two portions, theupper portion 124 lists some of the information entered in the display120 to indicate the parameters that the fatigue analysis tool utilizedto reach the results. The lower portion 126 contains the allowablestress (Ktσ) values for the specified Kc/Kt ratio values.

The user may select the “Summary” button in the upper portion 92 of thedisplay to receive a summary of the stress analyses performed by theautomated fatigue analysis method, system and computer program productof one embodiment of the present invention. When the user requests asummary of the stress analyses, the fatigue analysis manager agent 36automatically determines the margin of safety or any other predefinedcalculation, using the results of the stress analyses. The display ofFIG. 11 is then generated by the web server, transmitted to the clientcomponent and presented to the user via the interface 28. The displayhas four portions, the top portion 128 depicts the information regardingthe element and forces acting upon the element that were selected orentered by the user in display 96 of FIG. 6. The next portion 130depicts the results of the detail stress analysis as shown in display100 of FIG. 7. A fatigue allowable summary 132, which is also part ofthe overall summary, is similar to the display 122 of FIG. 10, but theallowable stress result is based on the same Kc/Kt ratio determined inthe detail stress analysis, 0.06. Since the allowable stresses weredetermined at 1.0, 0.5 and 0.0 in this example, the fatigue analysismanager agent 36 performs an iteration to arrive at the allowable stressfor 0.06 based upon the allowable stresses at 0.0 and 0.5 Kc/Kt ratios.The stress values used in the margin of safety calculation and theresult of the margin of safety calculation performed by the fatigueanalysis manager agent 36 are displayed in portion 134. Based upon theresults of the fatigue analysis and/or subsequent calculations, such asmargin of safety, the designers of the element and structure may adjustthe dimensions and/or material composition of the element to producemore desirable fatigue analysis results.

Therefore, the automated fatigue analysis method, system and computerprogram product of the present invention automatically provide the userwith the results of the fatigue analysis tool without requiring anyfurther manual input, that the user be specially trained to use thespecific fatigue analysis tool, or that the user be in the same physicallocation as the fatigue analysis tool.

The system 20 of the present invention and, in particular, the clientinterface 28, active server pages 30, fatigue analysis manager module32, fatigue analysis manager service 34, fatigue analysis manager agent36, database 38, and fatigue analysis tools, are typically embodied by aprocessing element and an associated memory device, both of which arecommonly comprised by a computer or the like. As such, the system of thepresent invention generally operates under control of a computer programproduct to provide the functionality described hereinabove inconjunction with the various components of the system, according toanother aspect of the present invention. The computer program productfor performing the contingent claim valuation includes acomputer-readable storage medium, such as the non-volatile storagemedium, and computer-readable program code portions, such as a series ofcomputer instructions, embodied in the computer-readable storage medium

In this regard, FIGS. 1-4 are block diagrams, flowcharts or otherschematic representations of methods, systems and program productsaccording to the invention. It will be understood that each block orstep of the flowchart, and combinations of blocks in the flowchart, canbe implemented by computer program instructions. These computer programinstructions may be loaded onto a computer or other programmableapparatus to produce a machine, such that the instructions which executeon the computer or other programmable apparatus create means forimplementing the functions specified in the flowchart block(s) orstep(s). These computer program instructions may also be stored in acomputer-readable memory that can direct a computer or otherprogrammable apparatus to function in a particular manner, such that theinstructions stored in the computer-readable memory produce an articleof manufacture including instruction means which implement the functionspecified in the flowchart block(s) or step(s). The computer programinstructions may also be loaded onto a computer or other programmableapparatus to cause a series of operational steps to be performed on thecomputer or other programmable apparatus to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide steps for implementingthe functions specified in the flowchart block(s) or step(s).

Accordingly, blocks or steps of the flowchart support combinations ofmeans for performing the specified functions, combinations of steps forperforming the specified functions and program instruction means forperforming the specified functions. It will also be understood that eachblock or step of the flowchart, and combinations of blocks or steps inthe flowchart, can be implemented by special purpose hardware-basedcomputer systems which perform the specified functions or steps, orcombinations of special purpose hardware and computer instructions.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions andthe associated drawings. As such, the Raptor, LifeWorks and StressCheckapplications are provided as specific examples of types of fatigueanalysis tools, however, the automated fatigue analysis of an element asprovided by the method, system and computer program product of thepresent invention may use other appropriate types of fatigue analysistools to create the load spectrum, determine the allowable stress anddetermine the actual stress for an element of an aircraft or otherstructure in order to perform margin of safety or any other type offatigue analysis. Therefore, it is to be understood that the inventionis not to be limited to the specific embodiments disclosed and thatmodifications and other embodiments are intended to be included withinthe scope of the appended claims. Although specific terms are employedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation.

That which is claimed:
 1. A method for automated fatigue and structuralanalysis of a structural element, the method comprising: receivinginformation regarding the structural element and a request to performfatigue and structural analysis upon the structural element;automatically performing at least two types of fatigue and structuralanalysis based upon the information regarding the element and therequest without further manual input, wherein automatically performingcomprises automatically selecting at least one analysis tool from aplurality of analysis tools to perform the at least two types of fatigueand structural analysis based upon the request; and automaticallyproviding results of the fatigue and structural analysis.
 2. The methodof claim 1, further comprising formatting the information receivedregarding the structural element prior to performing the fatigue andstructural analysis.
 3. The method of claim 1, wherein saidautomatically performing at least two types of fatigue analysiscomprises automatically determining a fatigue allowable for thestructural element and automatically determining an actual maximumstress for the structural element; and wherein the method furthercomprises automatically comparing the fatigue allowable and the actualmaximum stress and determining a margin of safety for the structuralelement based upon the comparison.
 4. The method of claim 3, whereinautomatically determining the fatigue allowable for the structuralelement comprises determining an anticipated loading of the structuralelement over time and determining the fatigue allowable to which thestructural element may be subjected based upon the anticipated loadingof the structural element over time, and wherein automaticallydetermining the actual maximum stress for the structural elementcomprises determining the actual stress to which the structural elementis subjected based upon the application of a reference load.
 5. Themethod of claim 1, further comprising storing the results of the fatigueand structural analysis.
 6. The method of claim 1, wherein receivinginformation regarding the structural element and the request to performfatigue and structural analysis upon the structural element comprisesreceiving information regarding the structural element and a request toperform fatigue and structural analysis upon the structural element froma plurality of distributed clients, and wherein the method furthercomprises transmitting the information regarding the structural elementand the request to perform fatigue and structural analysis from theplurality of distributed clients to at least one common processingcomponent via a computer network.
 7. The method of claim 6, furthercomprising presenting at least one web page upon each client to solicitthe information regarding the structural element.
 8. An automated systemfor fatigue and structural analysis of a structural element, the systemcomprising: a client component capable of receiving informationdescribing the structural element and a request for fatigue andstructural analysis of the structural element; and a processingcomponent responsive to said client component and capable ofautomatically performing the fatigue and structural analysis based uponthe information describing the structural element and the requestwithout additional manual input by automatically selecting at least oneanalysis tool from a plurality of analysis tools to perform the at leasttwo types of fatigue and structural analysis based upon the request,said processing component also capable of automatically providingresults of the fatigue and structural analysis to said client component.9. The system of claim 8, wherein said processing component is furthercapable of formatting the information for the fatigue and structuralanalysis.
 10. The system of claim 8, wherein said processing componentautomatically performs the fatigue analysis by: automaticallydetermining a fatigue allowable for the structural element;automatically determining an actual maximum stress for the structuralelement; automatically comparing the fatigue allowable with the actualmaximum stress; and automatically determining a margin of safety for thestructural element based upon the comparison.
 11. The system of claim10, wherein said processing component automatically determines thefatigue allowable for the structural element by determining ananticipated loading of the structural element over time and thendetermining the fatigue allowable to which the structural element may besubjected based upon the anticipated loading of the structural elementover time, and wherein said processing component automaticallydetermines the actual maximum stress for the structural element bydetermining the actual stress to which the structural element issubjected based upon the application of a reference load.
 12. The systemof claim 8, further comprising a storage element for storing the resultsof the fatigue and structural analysis.
 13. The system of claim 8,wherein said client component and said processing element are remotefrom one another, and wherein the system further comprises a computernetwork for interconnecting said client component and said processingelement.
 14. The system of claim 13, further comprising a plurality ofdistributed client components interconnected to said processing elementvia said computer network.
 15. The system of claim 14, wherein saidprocessing element comprises a server.
 16. The system of claim 13,wherein said client component is capable of presenting at least one webpage to solicit the information regarding the structural element.